Gravity refrigerant recirculation

ABSTRACT

A feed accumulator receives liquid refrigerant from the receiver and feeds it by gravity to the evaporator. Excess liquid refrigerant from the evaporator is temporarily stored in a lower level tank from which it is, from time to time, forced back to the accumulator by high-pressure refrigerant. Automatic controls and oil separator features are included.

lllite [151 ame Garland! 1 lieh. 22, 11972 54] GRAVITY RIEFMHGIERANT2,952,137 9/1960 Watkins ..62/174 1 1 2,978,877 4/1961 Long ..62/1743,164,973 1/1965 Watkins ..62/174 [72] Inventor: Milton W. Garland,Waynesboro, Pa.

. Primary Examiner-Meyer Perlin Company waynesbom' Attorney-A. YatesDowell and A. Yates Dowel], Jr. [22] Filed: Sept. 11, 1197111 [57] SC'llI21] Appl. No.: 711,487

A feed accumulator receives liquid refrigerant from the receiver andfeeds it by gravity to the evaporator. Excess [52] U.S. 1C1 ..62/174,62/218, 62/512 li uid refrigerant from the evaporator is temporarilystored in [51] int. Cl ..FZSb 11/00 a lower level tank from which it is,from time to time, forced [58] Field oi Search ..62/218, 174, 512 backto the accumulator by high-pressure refrigerant. Automatic controls andoil separator features are included. [56] References Cited UNITED STATESPATENTS 2,590,741 3/1952 Watkins ..62/174 6 (Ilaims, 3 Drawing FiguresGRAVITY REFRIGERANT RECIRCIULATION BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates to refrigeration and moreparticularly to the circulation of refrigerant in a system in which themaintenance of the necessary head for flooding of the evaporator isaccomplished by gravity.

2. Description of the Prior Art Gravity feed of evaporators has beenused for approximately 40 years. The refrigerant from the evaporator isreturned to an accumulator which separates liquid from vapor andprevents liquid from passing into the compressor. Since the evaporatoris flooded, it is necessary that the refrigerant which is not vaporizedbe transferred to the accumulator. However, the latter ordinarily isremote from and located above the evaporator, thus necessitating apressure head to move the liquid. This pressure head when used with asystem operating at low temperature levels imposes a penalty on thesystem which may be as much as 5 to 7 F.

Prior systems in which an accumulator has been used as as means fortransferring liquid back to the receiver are exemplified in US. Pats.such as Garland No. 1,954,695; Phillips No. 2,570,979; Sloan et al. No.2,655,008; Christiansen No. 2,778,195; Kocher et al. No. 2,836,966;Richards et al. No. 2,871,673; Wood No. 2,986,898; Grant No. 3,214,932;Ross No. 3,315,484; Garland No. 3,353,367; and Grant No. 3,487,656. GayU.S. Pat No. 1,994,037, discloses a system in which liquid from theaccumulator flows into the evaporator and a portion is returned to theaccumulator by using the expanded refrigerant as a propulsion means.

SUMMARY OF THE INVENTION The present invention is a refrigerating systemhaving a feed accumulator which supplies liquid refrigerant by gravityto a flooded evaporator which returns refrigerant vapors to theaccumulator and discharges liquid refrigerant into a drain separator andthen to a transfer tank by gravity. When the transfer tank is filled toa predetermined capacity, automatically controlled valves will diverthigh-pressure vapors into the transfer tank to return the liquidrefrigerant therein to the feed accumulator.

It is an object of the present invention to provide an improvedrefrigeration system in which a feed accumulator is provided in theliquid line from the receiver and from such feed accumulator to thecompressor, Which is positioned to provide the necessary gravity headfor flooding the evaporator, and which has transfer means utilizinghigh-pressure vapor for returning unevaporated liquid to the feedaccumulator. Controls are provided for automatic operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram ofapreferred embodiment of the invention;

FIG. 2, a schematic of a modified form of the invention; and

FIG. 3, a schematic of the control circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With further reference to thedrawings, the refrigeration system illustrated includes a compressor 1!)with the suction line 11 and discharge line 12, and condenser 13connected by line 14 to receiver 15 which is connected by line 16 tofeed accumulator17.

Feed accumulator 17 has a liquid supply line 29 connected to a header21. The header 21 may supply any desired number of evaporators, as forexample through lines 22, 23 and 24. lllustrative is evaporator 25 whichis connected to line 23. A check valve 28 is provided in line 23 andcheck valves 29 and 30 in lines 22 and 24 respectively. Throttling orexpansion valve 29 is positioned in line 23 just ahead of evaporator 25.

Feed accumulator 17 is positioned at a sufficient elevation above theevaporators to produce a desired flow rate therein and to maintain themin flooded condition. The head of refrigerant within the feedaccumulator is determined by the height of a float 32 connected by line33 to a selected portion of the accumulator and by line 34 to the liquidline 20 beneath the accumulator. FLoat 32 controls solenoid valve 36 inline 16 to regulate the refrigerant supply from the receiver to the feedaccumulator. .Iust beyond the valve 36 is a modulating or throttlingvalve 38. Any selected type of refrigerant feed control, such as amechanical float or a thermal level control, may be used instead of afloat switch operated solenoid valve.

From the evaporator refrigerant vapors and Unevaporated liquidrefrigerant leave through line 40 having valve 41 therein. Return line42 rises to transport the vapors back to feed accumulator 117 from whichthey may enter suction line 111..

Unevaporated liquid refrigerant falls in line 44 into drain separator 46from which it gravitates through line 43 having valve 49 therein intotransfer tank 50.

Transfer tank 50 has upper and lower float switches 51 and 52,respectively. When the liquid level in the transfer tank is sufficientlyhigh, the upper float switch 51 operates causing pilot solenoid valve53, which is normally closed, to open. Valve 53 is located in ahigh-pressure vapor line 12' from the compressor and when valve 53 isopen, high-pressure refrigerant vapor is carried by line 54 to thenormally open valve 49, applying pressure to its operating pistonthereby closing valve 49 and stopping the flow of liquid refrigerantthrough the line 43.

Branch line 55 is connected to line 12 and line 54 at one end, and isconnected at its other end to line 44 and has a solenoid controlled ventvalve 57 therein which is normally open. Line 12 has a branch line 60which is connected at its other end to branch 61 which is connected tothe operating pressure switch in the normally open valve 41 in line 40and to branch 62 which is connected through normally open solenoidcontrolled vent valve 63 to line 42.

Flow through line 69 is controlled by normally closed solenoid operatedvalve 64. Line 68 is connected at one end to the discharge line 40 fromthe evaporator and at its other end to line 62 intermediate valves 64and 63.

Branch line 65 is connected to line 23 at one end and is connected atits other end to the top of drain separator 46 and has a pressureregulating valve 67 therein.

Line 12' also has branch line 70 connected through normally closedsolenoid operated control valve 71 to the upper portion of transfer tank50.

When the liquid level in transfer tank 59 is high enough, float switch51 is closed to energize a relay R11 (FIG. 3) which in turn energizesthe coil of high-pressure valve 53 and causes such valve to open, thusadmitting high-pressure vapor from line 12 to line 54, applying pressureto the operating piston of normally open valve 49-, closing valve 49'.Relay R1 also energizes a holding switch 72 in the circuit of the lowerfloat switch 52 and the coils of vent valve 57 and control valve 71 toclose valve 57 and open valve 71. This permits high pressure vapor toenter transfer tank 50 through line 12 and branch line 74), forcingliquid refrigerant through return line and check valve 81 into the feedaccumulator 17.

As the liquid level recedes in the transfer tank 50, the float switch511 will open, but the switch 72 will continue to energize the relay R1.When the liquid level in transfer tank 50 falls below the lower flatswitch 52, such switch will interrupt the flow of electrical energy tothe relay R1 and deenergize such relay. This causes the solenoidoperated control valve 71 and high-pressure valve 53 to close and causesvent solenoid valve 57 to open. Valve 49 opens due to spring action andrelease of the high-pressure vapor.

Thus the foregoing operation accomplishes a normal operation of theevaporator with the only pressure head imposed on it being that of thedesign pressure for flow of the vapors generated and any excess liquid.Valve 29 need only be preset once in order to adjust the refrigerantflow rate for the evaporator 25 at the design operation levels.

If desired, thermostat 85 may be provided responsive to the coolingaction of evaporator 25 causing solenoid valve 86 to close in order tostop refrigerant flow and prevent an excessive accumulation of liquidrefrigerant in the evaporators under conditions of no load.

With the use of additional evaporators as indicated in dotdash lines,through lines 22, 24, any of these may be selectively defrosted withoutinterfering with the performance of the remainder of the system. Inorder to carry out defrosting, switch 90 (FIG. 3) is placed in the Onposition and this energizes a relay R2 and simultaneously causes thehigh-pressure vapor solenoid operated valve 64 to open. Relay R2 opens aswitch 73 and causes the vent solenoid valve 63 to close, therebyforcing high-pressure vapor through branch line 61 and the dischargeline 68. The increased vapor pressure in the branch line 61 causes thenormally open valve 41 to close and increased pressure in the evaporator25 closes check valve 28. The pressure rises to appropriate pressuretemperature level of the refrigerant being used in order to causemelting of the frost from the evaporator surfaces.

The pressure regulating valve 67 responds to the increased pressurewithin the evaporator and passes liquid refrigerant from the evaporatorinto the drain separator 46. The operation of the liquid transfer systemwill respond to a high liquid level as previously described.

When defrosting is completed switch 90 is opened thereby causinghigh-pressure vapor solenoid 64 to close and deenergizing the relay R2to permit vent solenoid 63 to open. This permits valve 41 to open andwith the pressure released check valve 28 opens and evaporator 25 isagain in service.

The accumulator is designed for improved oil separation. Liquidrefrigerant from the receiver line 16 and from line 80 enter theaccumulator at one end, indicated as the left end in the drawing. Theaccumulator is of substantial horizontal dimension having a main bottom17 and a reservoir 17" which is substantially sunken below the level ofthe main bottom. The reservoir is located adjacent to one end or side ofthe accumulator remote from the end at which the liquid refrigerantenters. The liquid outlet or supply line 20 is positioned near the endof the accumulator such that liquid refrigerant entering from the lines16 and 80 flows across reservoir 17". The outlet 20' ofthe pipe 20projects above the bottom surface of the accumulator in order to avoidreceiving oil and possibly other foreign matter.

From the bottom of reservoir 17' a discharge pipe 90 is connectedthrough valve 91 to oil separator 92 having a drain valve 93 at itslower portion. From the upper portion vapor line 94 having valve 95therein is connected to return the refrigerant vapor which has beenseparated from the oil to the top of the accumulator.

In the modification of FIG. 2, the location of the drain separator andtransfer tank is different than in FIG. 1. In FIG. 1 the drain separator46 is at a lower level than evaporator 25 and transfer tank 50 is at alower level than the drain separator. However, in FIG. 2 drain separator46' is just below the outlet of the evaporator and the transfer tank 50has its vertical center on the same level as the bottom of the drainseparator 46. Even though the levels are shifted, the principle ofoperation of the modified form is the same. However, the drain separatorand transfer tanks required for FIG. 2 may need to be slightly largerthan those in FIG. 1 for the same volume of liquid transfer. Theevaporator, drain separator and transfer tank may be located as desiredprovided that there is sufficient difference in level for the necessarygravity flow.

I Claim:

1. In a refrigeration system having means for supplying liquidrefrigerant and for compressing and condensing refrigerant vapor, a feedaccumulator having an inlet from the supplying means for liquidrefrigerant and an outlet to the compressing means for vapor, anevaporator connected to the feed accumulator, the feed accumulatorpositioned at a higher elevation than the evaporator, a first line formthe accumulator to the evaporator for supplying liquid refrigerantthereto, a second lme from the evaporator to the accumulator forreturning a refrigerant vapor to the accumulator, a drain separator anda transfer tank, said drain separator connected to said second line andpositioned at a level to receive liquid refrigerant from said secondline by gravity flow, said transfer tank connected to said drainseparator and positioned to receive liquid refrigerant from said drainseparator by gravity flow, means connecting the transfer tank to theupper portion of said accumulator, liquid level responsive means in thetransfer tank, and means for connecting high-pressure vapor from thecompressing means to the transfer tank for forcing liquid refrigeranttherefrom into the feed accumulator.

2. The invention of claim 1 and means for selectively connectinghigh-pressure vapor from the compressing means to the outlet of theevaporator, and means for permitting liquid refrigerant in theevaporator to discharge into the drain separator as it is subjected topressure from the high-pressure vapor.

3. The invention of claim 1 in which said transfer tank has upper andlower liquid level responsive means, said upper level liquid responsivemeans controlling valve means which connects the high-pressure vaporfrom the compressing means to the transfer tank and said lower liquidlevel responsive means operating to interrupt the flow of high-pressurevapor to the transfer tank.

4. The invention of claim I in which said first line is connected to thefeed accumulator at a position which is laterally remote from theconnection of said second line to the accumulator, and said feedaccumulator has a well intermediate the said two connections for thecollection of oil, oil separator means connected to said well, and meansconnecting the upper portion of the oil separator means to the upperportion of the feed accumulator for the return of any refrigerant vaporthereto.

5. The invention of claim 1 including pressure operated valve meansbetween said drain separator and said transfer tank, and means forclosing said pressure operated valve means by the high-pressure vaporfrom said compressor.

6. The invention ofclaim 1 including float control means for controllingthe liquid level in said feed accumulator.

1. In a refrigeration system having means for supplying liquid refrigerant and for compressing and condensing refrigerant vapor, a feed accumulator having an inlet from the supplying means for liquid refrigerant and an outlet to the compressing means for vapor, an evaporator connected to the feed accumulator, the feed accumulator positioned at a higher elevation than the evaporator, a first line form the accumulator to the evaporator for supplying liquid refrigerant thereto, a second line from the evaporator to the accumulator for returning a refrigerant vapor to the accumulator, a drain separator and a transfer tank, said drain separator connected to said second line and positioned at a level to receive liquid refrigerant from said second line by gravity flow, said transfer tank connected to said drain separator and positioned to receive liquid refrigerant from said drain separator by gravity flow, means connecting the transfer tank to the upper portion of said accumulator, liquid level responsive means in the transfer tank, and means for connecting highpressure vapor from the compressing means to the transfer tank for forcing liquid refrigerant therefrom into the feed accumulator.
 2. The invention of claim 1 and means for selectively connecting high-pressure vapor from the compressing means to the outlet of the evaporator, and means for permitting liquid refrigerant in the evaporator to discharge into the drain separator as it is subjected to pressure from the high-pressure vapor.
 3. The invention of claim 1 in which said transfer tank has upper and lower liquid level responsive means, said upper level liquid responsive means controlling valve means which connects the high-pressure vapor from the compressing means to the transfer tank and said lower liquid level responsive means operating to interrupt the flow of high-pressure vapor to the transfer tank.
 4. The invention of claim 1 in which said first line is connected to the feed accumulator at a position which is laterally remote from the connection of said second line to the accumulator, and said feed accumulator has a well intermediate the said two connections for the collection of oil, oil separator means connected to said well, and means connecting the upper portion of the oil separator means to the upper portion of the feed accumulator for the return of any refrigerant vapor thereto.
 5. The invention of claim 1 including pressure operated valve means between said drain separator and said transfer tank, and means for closing said pressure operated valve means by the high-pressure vapor from said compressor.
 6. The invention of claim 1 including float control means for controlling the liquid level in said feed accumulator. 